1. Technical Field
The present invention relates to a virtual network connection method, a network system, and a network device, and more particularly to a virtual network connection method, a network system, and a network device for connecting respective networks to each other.
2. Related Art
Up to now, there has been known a technique called Virtual Private Net work (VPN) in which networks at remotely separated hubs (hereinafter referred to as “hub networks”) are connected by the aid of a network (hereinafter referred to as “core network”) of a service provider. The service provider provides a service that connects the hub networks of plural customers to each other in the core network, and disables a communication between different customers to construct networks with individual customers independent from each other.
As techniques for connecting between the hub networks by the aid of the core network, there are a technique called “media access control (MAC-in-MAC)” represented by provider backbone bridges (PBB) disclosed in “IEEE802.1ah Provider Backbone Bridges”, multi protocol label switching (MPLS) disclosed in “RFC4364 BGP/MPLS IP Virtual Private Networks”, and virtual private LAN service (VPLS) disclosed in “RFC4762 Virtual Private LAN Service (VPLS) Using Label Distribution Protocol (LDP) Signaling”.
The MAC-in-MAC is a technique in which the hub networks of the customers and the service provider are layer-2-connected (second layer in an OSI reference model), and a layer 2 communication is enabled between the respective hub networks. Within the core network, unicast, flooding, multicast, and broadcast data are forwarded by a technique of the layer 2. The device of the service provider adds a layer 2 header in a format of the packet MAC-in-MAC to a packet that has arrived at an edge device (device of a service provider connected to hub networks of customers) from a certain hub network. The core network forwards the packet by the aid of the added header therein. Then, the core network deletes the added layer 2 header when finally delivering the packet to the hub network through the edge device which is an exit of the core network, and delivers the packet to the hub network of a destination. The layer 2 header of the packet of the customer and information on a layer 3 or higher are forwarded without any change to enable the layer 2 communication between the hub networks, which is a feature of the MAC-in-MAC. The connection of the service provider and the hub networks does not depend on the layer 3. The MAC-in-MAC can conduct the network operation and management at low costs as compared with the MPLS and the costs of the device are frequently relatively inexpensive because of no use of a specific protocol for forwarding the packets between the hubs within the core network. However, the edge device of the core network needs to hold all of information on the layer 2 such as MAC address learning, and needs to be a device that can hold large volume information.
In the MPLS, as the method of connecting between the hub networks of the customers and the service provider, there are a layer 3 method (third layer in the OSI reference model) disclosed in “RFC4364 BGP/MPLS IP Virtual Private Networks”, and a layer 2 method disclosed in “RFC4762 Virtual Private LAN Service (VPLS) Using Label Distribution Protocol (LDP) Signaling”. Those respective methods enable the connection between the networks of the layer 3 connection, and the connection between the networks of the layer 3 connection. The MPLS determines two labels of a first label indicative of destinations within the core network and a second label indicative of destinations of the hub networks according to a protocol using a border gateway protocol (BGP), within the core network. The MPLS forwards the packets within the core network by the aid of those labels. The device of the service provider adds an MPLS header including the first label and the second label to the packet that has arrived at the edge device from the certain hub network. The core network forwards the packet by using the added header therein. Then, the core network deletes the added MPLS header when finally delivering the packet to the hub network through the edge device which is an exit, and delivers the packet to the hub network of the destination. The layer 3 connection has one of the features that routing between the hubs of the customers is mediated by the service provider to facilitate the layer 3 connection of the customer. The layer 2 connection has one of the features that the layer 2 header and the information on the layer 3 or higher are forwarded to the packet of the customer without any change to enable the layer 2 communication between the hub networks. In that case, the connections between the service provider and the hub networks do not depend on the layer 3. The MPLS needs to operate and manage a complicated protocol, the costs are liable to increase, and the costs of the device are also frequently relatively expensive, because the protocol of the BGP or the MPLS is used to forward the packets between the hubs within the core network. Also, the edge device of the core network needs to hold multiple pieces of information including the label information, and needs to be a device that can hold large volume information.
A VPN using the MAC-in-MAC or the MPLS needs to conform the connection mode to any one of the layer 3 connection and the layer 2 connection in the connection between the hub networks of the customers and the core network of the service provider, for configuration of the VPN.